spread evenly onto beef steak. Combine bread crumbs and parsley in another small bowl. Pat mixture evenly over mustard mixture. Place steak on rack in shallow roasting pan. Insert ovenproof meat thermometer so tip is centered in thickest part of beef, not resting in fat. Do not add water or cover. Roast steak and potatoes in 425°F oven 25 min.; turn potatoes. Continue roasting 15-20 min. to medium rare (145°F) to medium (160°F) doneness for steak and until potatoes are tender.